1Harm H. Tillema and Karl Smith "learning from portfolios: differential use of feedback in portfolio construction" Studies in Education Evaluation 26( 2000 ) .193-210
2H.H.Tillema "design and validity of a portfolio instrument for professional training" Studies in Education Evaluation 24( 1998 ).263-278
3Dominique M.A.Sluijsmans,George Moerkerke,Jeroen J. G. Van Merrienboer and Filip J. R. C. Dochy "Peer Assessment in Problem Based Learning"Studies in Education Evaluation 27 (2001).153-173.
